Conventionally, insulation is removed from scrap copper wire by burning or by mechanical stripping processes. These have disadvantages particularly with respect to fine copper wire. In the burning process undesirable ecological effects are produced and fine copper wire tends to be oxidized. The stripping process is not particularly satisfactory for smaller wire.
The present invention provides a continuous process for removing a gas producing insulation from an item such as copper wire and particularly for removing insulation containing polyvinyl chloride. This type insulation when subjected to a conventional pyrolysis or vaporization process produces chlorine. The chlorine is produced either as a gas or more likely as hydrochloric acid, as water vapor is present in the products of decomposition or combustion. Both of these are undesirable products from an ecological point of view.
As used in this application the term chlorine includes the gas and the acid form. The present process provides for the reaction of the hydrochloric acid (HCl) with a calcium containing substance such as calcium oxide, calcium carbonate, dolomite (part MgCO.sub.3 and part CaCO.sub.3), and the like, to produce calcium chloride as a by-product. The calcium chloride is used by many street and highway departments to apply to snow and ice covered streets and highways. The present process has the advantage that there are no undesirable by-products, and the emissions are conventional such as hot air, nitrogen, water vapor, and carbon dioxide.
Accordingly, one of the principal objects of the present invention is to provide a continuous process for removing insulation containing polyvinyl chloride from items such as copper wire without the formation of undesirable chlorine containing by-products. Another object is to provide an economical process which operates continuously and which produces cleaned copper wire from the process. Still another object is to provide a reaction method whereby copper wire coated with polyvinyl chloride insulation is passed through a heated fluidized bed of small particles of calcium carbonate to decompose the insulation and react the chlorine from the insulation with the calcium carbonate to produce usable calcium chloride.
These and other objects and advantages will become apparent hereinafter.